Cooling apparatus



p 25, 1962 D. H. DENNIS 3,055,192

COOLING APPARATUS Filed Dec. 1, 1960 INVENTOR DAVID M. osums ATTORNEY 3,055,192 COOLENG APPARATUS David H. Dennis, Short Hills, N..l'., assignor to Specialties Development Corporation, Eelleville, N.J., a corporation of New Jersey Filed Dec. 1, 1960, Ser. No. 73,092 4 Claims. (Cl. 62-440) The present invention relates to refrigeration, and, more particularly, to improved apparatus for maintaining an element at a much lower temperature than the ambient temperature.

Heretofore, it has been found that, by cooling elements such as infrared cells and the like to a temperature of about 100 F. or lower, the sensitivity of the cell is increased and the noise to signal ratio of the cell is greatly decreased. It has been proposed to accomplish this by expanding a refrigerant under pressure in the vicinity of the cell and returning the cool expanded refrigerant in regenerative heat exchange with the incoming refrigerant to cool the refrigerant before expansion and thereby attaining a greater Joule-Thomson effect.

For certain applications, liquefied carbon dioxide has been utilized as the refrigerant because of its high storage density. However, since cool carbon dioxide and certain other refrigerants, when expanded at low temperatures, form snow-like particles or solidify at or within the expan sion nozzle to block the same, it has been proposed to attach one end of a heat conductive wire in heat conducting relation at the nozzle and connect the other end of the wire to a heat source located externally of the apparatus. The heat conducted by the Wire is effective to sublime the solidified refrigerant and unblock the nozzle.

Heretofore, it has been customary to have the wire extend through the expanded refrigerant return flow passageway which caused the wire to be cooled and lower its heat conducting effectiveness whereby the external end of the wire was required to be connected to a sufficiently large heat source to conduct the necessary heat to unblock the nozzle.

Accordingly, an object of the present invention is to provide improved cooling apparatus adapted to utilize carbon dioxide or other refrigerants which form snow-like particles which requires a much smaller heat source to provide the necessary heat for the wire.

Another object is to provide such apparatus which provides for more efiicient regenerative or counter-current heat exchange by reason of its construction and arrangement.

A further object is to provide such apparatus which is simple and economical in construction and is practical and reliable in operation.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

A preferred embodiment of the invention has been chosen for purposes of illustration and description, and is shown in the accompanying drawing, forming a part of the specification, wherein:

FIG. 1 is a longitudinal sectional view of cooling apparatus in accordance with the present invention.

FIG. 2 is an enlarged end view of the cooling assembly.

FIG. 3 is a fragmentary plan view taken on FIG. 2.

Referring to the drawing in detail, cooling apparatus is shown which generally comprises a tubular, double-wall evacuated glass envelope, such as a Dewar tube for an infrared cell having an inner end wall 11, and a light sensitive element 12 within the envelope adjacent the inner side of the end wall 11; and a cooling assembly 14 3,055,192 Patented Sept. 25, 1962 ice envelope by an electrically conductive strip 17 plated onto the outer side of the inner wall of the envelope.

The cooling assembly 14 generally comprises a tubular member or sleeve 18, a capillary tube 19 mounted on the sleeve 18 in the manner about to be described having an inlet 20 and an outlet or nozzle 21, a fitting 22 which serves as a heat source or sink and is secured to the outer end of the sleeve 18 for connecting the inlet 20 to a source of refrigerant (not shown), and a heat conductive wire 24 extending through the sleeve 18 and having its inner and outer ends attached in heat conducting relation to the tube 10 near its outlet and to the fitting 22, respectively.

The sleeve 18 preferably is constructed of heat insulating material for the purpose made apparent hereinafter. The sleeve has a large central bore 25 to reduce the weight thereof which is formed with a wall 26 near its inner end provided with a small aperture 27, a pair of opposite slots 28 at its inner end and a pair of opposite openings 29 between the slots, and a counter-bore 30 at its outer end for receiving the fitting 22.

The fitting 22 is formed of metal and comprises a body 31 and a threaded nipple 32 each having a central bore portion 34' and 35 respectively, and a hollow radially slotted plug-shaped portion 36 which is threadedly secured in the counter-bore 30 of the sleeve 18.

While the capillary tube 19 may be mounted on the sleeve in counter-flow or regenerative heat exchange relation by spirally winding the same thereon to form a coil in the space between the inner side of the inner Wall of the envelope and the outer wall of the sleeve 18 which space serves as the return flow passageway, the efiective length of the heat exchange surface area thus provided can be greatly increased by first spirally winding the capillary tube 19 on a mandrel wire 37 and then spirally winding this assembly on the 'sleeve 18.

It was found that a highly efiicient heat exchange assembly could be provided by elements having the following approximate dimensions and characteristics:

Radial space:

(between sleeve 18 and inner wall of Dewar) 0.047 inch. Wire 24:

Material Copper. Diameter 0.025 inch. Overall length 2.5 inches.

'In assemblying the heat exchanger or cooler, the outer end portions of the capillary tube 19, the heat conducting wire 24 and the mandrel wire 37 extend through and are secured in the bore portion 34 of the fitting body 31 by a mass of heat conductive material, and the outer end of the tube 19 extends through the bore portion 35 of the 3 fitting nipple 32 with its inlet 20 flush with the outer end of the nipple. The assembly provided by the tube 19 and the wire 37 exits through a slot 38 in the fitting plug portion 36, and is coiled about the sleeve 18 to the inner end thereof.

The heat exchange wire 24 extends through the bore 25 of the sleeve 18 spaced from the inner Wall thereof to provide for maximum insulation thereof to prevent heat loss, passes through the aperture 27 of the wall 26 wherein it is secured, and exits through one of the slots 28 at the inner end of the sleeve 18.

The mandrel wire enters one of the openings 29, is anchored on the wire 24, exits through the other opening 29 and is wound about the sleeve 18 to anchor the same.

The portion of the heat conducting wire 24 which extends outwardly through one of the slots 28 is flattened and is wrapped around the outlet end of the capillary tube near its outlet 21 in heat exchange relation to conduct ambient heat from the fitting 22 to the outlet end of the tube 19 to thaw out any refrigerant which has frozen and has blocked the outlet.

In operation, the refrigerant enters the inlet 20 of the tube 19 and exits at its outlet 21 and cools the end wall 11. The expanded refrigerant returns by way of the space between the sleeve 18 and the inner side of the inner wall of the envelope and cools the incoming refrigerant in the tube 1.9 by heat exchange relation as it flows to the outer end of the heat exchange assembly and exits to the atmosphere.

By the time the spent refrigerant reaches the fitting 22, it has been warmed up suiiiciently by the incoming refrigerant so as not to cool the fitting and minimize its heat source effectiveness. The heat conducting wire is not cooled because it is insulated from the exchanger by the sleeve 18. In this manner the light sensitive element 12 can be constantly and uniformly maintained at a temperature of about minus 100 F. by using carbon dioxide as the refrigerant.

From the foregoing description, it will be seen that the present invention provides extremely compact and highly eflicient cooling apparatus which maintains a constant and uniform low temperature and unblocks itself upon fireeze-up.

As various changes may be made in the form, construction and arrangement of the parts herein, without depart- 45 2,952,141

ing from the spirit and scope of the invention and Without sacrificing any of its advantages, it is to be understood that all matter herein is to be interpreted as illustrative and not in any limiting sense.

I claim:

1. In cooling apparatus, the combination of a tubular housing having an open end and a wall at the other end providing a chamber located adjacent an element to be cooled; and an assembly dimensioned to be inserted within said housing comprising a heat insulating member having a bore, a coil formed of heat conductive capillary tubing mounted on said member having an inlet for refrigerant under pressure at said open end and having an outlet adjacent said wall for expanding the refrigerant within said chamber, a heat source located externally of said housing, and a heat conductive wire extending lengthwise through the bore of said member having one end attached in heat conducting relation to said tubing adjacent its outlet and having its other end attached in heat conducting relation to said heat source, said housing and said assembly having space therebetween along the length thereof to provide a passageway for conducting expanded refrigerant from said chamber to the open end of said housing.

2. In cooling apparatus according to claim 1, wherein said wire is flattened and wrapped around said tubing at said outlet.

3. In cooling apparatus according to claim 1, wherein said tubing is spirally wound on a mandrel wire arranged in a spiral about said tubular member, and said tubing has spaced apart adjacent convolutions and said assembly is fitted into said housing, whereby the space between convolutions, the inner Wall of said housing and said tubular member provide a spiral return flow passageway for expanded refrigerant.

4. In cooling apparatus according to claim 1, wherein said heat source is a metallic fitting means secured to said member for connecting a source of refrigerant to said inlet.

References (Iited in the file of this patent UNITED STATES PATENTS *Fong Sept. 6, 1960 Nelson et al. Sept. 13, 1960 

